If you want to unblock unknown calls but still want protection from spam, you don't have to leave yourself completely exposed. iOS allows third-party apps (like Truecaller, Hiya, or Nomorobo) to identify spam calls.
The most common reason iPhone users miss calls from numbers not in their contacts is the built-in feature. When this is active, calls from numbers not found in your contacts, Siri Suggestions, or recent outgoing calls are automatically silenced and sent to voicemail. unblock unknown calls iphone
Here is how to turn it off: